Abstract

RUIZ-MARIN, Alejandro et al. Biodegradation of wastewater pollutants by activated sludge coimmobilized with Scenedesmus obliquus. Agrociencia [online]. 2013, vol.47, n.5, pp.429-441. ISSN 2521-9766.

Wastewater treatment plants produce large quantities of biomass (sludge) that require about one-third of the total investment and plant operation costs for their treatment. With microbial immobilization and coimmobilization with microalgae, it is possible to handle high cell concentration in the column reactor and increase its efficiency. The experimental design consisted in immobilized and coimmobilized S. obliquus with activated sludge in alginate beads cultured under continuous light or photoperiods (12 h/12 h) in artificial wastewater medium to evaluate the growth, nutrients and biochemical oxygen demand (BOD) removal. The results showed that the microalgae S. obliquus immobilized and coimmobilized in cultures under continuous light had higher growth rates (0.624 d^-1 and 0.552 d^-1) than under photoperiods (0.456 d^-1 and 0.312 d^-1). Also, a higher cell density (4X10⁶ cells bead^-1 and 2.9X10⁶ cells bead^-1) was obtained under continuous light than under photoperiods (2.0X10⁶ cells bead^-1 and 1.0X10⁶ cells bead^-1). The removal of nitrogen by S. obliquus, immobilized (92 %) and coimmobilized (60 %) under continuous light, was higher (40 %) than under photoperiods. Also, 43 % of BOD was removed by the coimmobilized system under continuous illumination. The coimmobilization system favored growth of algae and bacteria under continuous light, suggesting a possible exchange of gases (CO₂ and O₂): oxygen produced by microalgae and CO₂ by bacteria.

Keywords : activated sludge; coimmobilization; growth; Scenedesmus obliquus; nitrogen and organic matter removal.

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